The present invention relates to signal generators, and more particularly to generators of a plurality of signals with correction therefor.
In the field of radio-frequency communications or transmission of information, it has been a general practice to employ serial radio-frequency transmission to perform serial transmission of information to a remote receiver. Although such devices have served the purpose, they have not proven entirely satisfactory under all conditions of service because difficulty has been experienced in increasing data transmission rates with limited bandwidth available, a problem which is overcome by the present invention.
Serial radio-frequency transmission of information, wherein a single stream of bits is used to modulate a transmitter has limited capability. If more information must be transmitted within a fixed period of time, the data rate must be increased, which has several undesirable consequences. For example, higher data rates place more severe constraints on the components used to modulate the transmitter, which can result in higher cost. Furthermore, an increased data rate requires a higher receiver bandwidth, so that serial transmission is limited by the receiver's maximum bandwidth, a limitation which can be troublesome in the event of increased data requirements. A partially parallel digital radio-frequency uplink can provide increased data rates with savings in receiver bandwidth and in the modulation components of the transmitter. However, such implementation of multiple carriers would entail building several complete transmitters, each for example including a crystal oscillator and several tuned multiplication and amplification stages needed to produce the desired output power and frequency. Such an approach would use a large number of parts and waste valuable space, which can be especially disadvantageous where available space for the transmitter is limited. Also, accompanying each additional transmitter are additional required adjustments, resulting in cumbersomeness and inefficiencies.